“I don’t know anyone who can call this election,” asserts BBC director-general Lord Hall. Everyone agrees: this election is uncallable. Which is true enough about the outcome. But there are things we do know, or at least as good as know, will unfurl in 100 days’ time. Here are five of them:

1) Three-party politics is dead

Two-party politics has been dead for a while. Since February 1974, to be exact, when Jeremy Thorpe’s Liberals increased their support from 7.5 per cent in 1970 to 19.3 per cent. Since the, the Conservatives’ and Labour’s combined share of the vote only once surpassed 75 per cent. Of course if you live in Scotland or Wales, even three-party politics has long been a misnomer, thanks to the rise of their respective nationalist parties. (Northern Ireland is a category of its own.) But now the whole UK is united in its political fragmentation, with UKIP over-taking the Lib Dems and the Greens running my party close.

It is quite plausible that, this May, one-in-four voters will choose a party other than the ‘LibLabCon’ parties which have dominated Westminster politics for the past century or more. No-one is yet sure how to handle this disruption. Certainly not the broadcasters, whose chaotic attempts to arrange this year’s televised leaders’ debates have descended into free-for-all farce (Plaid Cymru given equal billing with the Lib Dems? The DUP, the fourth largest party in the Commons, ignored?). And certainly not our cumbersome electoral system, which looks likely to deny Ukip anything like the representation its poll rating will merit.

2) No party will win a (comfortable) majority

There is a slim chance either the Conservatives or Labour might surprise us, and sneak an absolute majority; the psephologists at Elections Etc estimate the probability at one-in-five. But the chances of a convincing majority are miniscule. For all that the Conservatives pray in aid John Major’s unexpected 1992 triumph, a majority of 21 or fewer is the stuff of nightmares for either David Cameron – or, indeed, Ed Miliband. Neither of them wants to be beholden to their rebellious nut-job elements – whether implacable Europhobes, or Unite-sponsored MPs looking to run on a manifesto to the left of Syriza – for survival in office.

In the circumstances, doing well enough but falling just short (let’s say being the single largest party, with at least 295 seats) could be the preferable outcome. After all, it would not only give the winner first dibs at forming the next government and remaining/becoming Prime Minister; but also give them the excuse they need to ditch those manifesto pledges to which the zealots are wedded but which put off the undecided voters. So the pragmatism of Thomas Cromwell, not the purism of Thomas More, remains the next government’s default mode. And, let’s be honest, that suits just fine those backbenchers who earn their constituency spurs by striking an independent pose.

3) The biggest single party will have to do a deal to survive

The arrival of multi-party politics, the high-likelihood of another hung parliament: Britain gets Borgen at last. Yet there seems scant appetite for Scandi-style deal-making between the parties. Part of this is the usual “we’re going all out for victory” mantra party leaders have to maintain this side of the election to pep up their activists (as well as to forestall smart-alec interviewers trying to pin them down on their policy red lines). For the Conservatives and Labour, both Cameron and Miliband realise their supporters want and expect them to deliver not just victory, but also then to implement an authentically blue/red programme of government. Talk of deals, of negotiation and compromise, is seen as conchy defeatism by their hard-working, pavement-pounding, envelope-licking troops on the ground.

For the other parties contemplating propping up the next government, the spectre of the Lib Dems’ fate in this parliament looms large. A junior partner’s lot is rarely a happy one, attacked on all flanks and worn down by the relentless bombardment. Yet if no one party gains a working majority, a deal there will have to be: the biggest single party will need to work with at least one other party to reach the magic 326 MPs to ensure they can form a government and get their guy into Number 10. Ad hoc deal-making, rather than formal coalition, might seem like a nice, easy option now (the grass is always greener), but give it a few months of knife-edge votes then let’s see how that hopey-changey arrangement looks like it’s working out. Whatever else can be said about the current Coalition, it has lasted the course intact.

4) The Lib Dems aren’t dead yet

All the pundit chatter is of the insurgent UKIP, Greens and SNP. Fair enough: their sudden emergence is new, its impact as yet unknown, so speculation can run riot. By contrast, the Lib Dems seem on the wane, so last election. Yet even the most gloomy forecasters reckon the Lib Dems will win at least 20 seats. (And I think those are serious under-estimates given Lord Ashcroft’s polling in our battleground seats showing the boost of incumbency.) In a hung parliament, this gives my party serious leverage, more than UKIP and the Greens combined will be able to muster.

This poses the serious question for us: do we try and use our parliamentary muscle within a formal coalition, or do we assert ourselves from outside government? If Nick Clegg remains leader, it’s likely he will try and steer the Lib Dems towards the former, arguing that being embedded within government is key to getting policy from our manifesto enacted as legislation. If he’s replaced by Tim Farron, though, the party’s likely to take a more oppositional stance, focusing on re-building its base and grabbing victories in parliament when the opportunity arises. Either way, the Lib Dems will matter for another five years.

5) Whoever governs will have a torrid time

Commentators often like to make the claim that “this is the election to lose”. In 2010, then Bank of England governor Mervyn King reportedly stated that “whoever wins this election will be out of power for a whole generation” because of how tough the fiscal austerity would have to be. That perhaps indicates why politicians rarely decide to refuse power on the basis of such predictions. As Tim Montgomerie pointed out last week, “It is interesting that ministers never want to give up their jobs. Most know what a difference they can make.” Always best to KBO, as Churchill would have resiliently exclaimed.

Either Prime Minister Cameron or Miliband will need plenty of that bulldog spirit to sustain them through to 2020 (assuming they can stick it that long). The Conservatives will have to square the circle that is their promise to hold an in/out EU referendum by December 2017. Winning the referendum will be the easy bit for Cameron; keeping his party united a whole lot more challenging (as I suggested here last year). Labour, though their spending plans have considerably more wiggle-room than George Osborne’s according to the IFS, will still have to find £7 billion of cuts and/or tax rises, not including any additional pre-election giveaways they may promise for the NHS or for students. After the past five years, that may sound a modest target, but even so it will almost certainly disappoint its supporters. So European splits and the spluttering economy will once again dominate the British political scene. It’s as if 1974 never went away.